This is relevant because 1) he started as Secretary of Defense after Hillary Clinton’s use of a personal email account became an issue and 2) the Defense Department won’t say when Carter stopped. From the A.P.:

The Pentagon acknowledged Wednesday that Defense Secretary Ash Carter used a personal email account to do some of his government business during his first months on the job.

Carter’s press secretary, Peter Cook, released a statement saying Carter believes his use of personal email for work-related business was a mistake. Cook declined to say whether it was a violation of Pentagon email policies. Cook said Carter stopped the practice, but Cook did not say when.

Why did Carter think it was OK in the first place? From the New York Times:

In a written statement on Wednesday, a spokesman for Mr. Carter said that the defense secretary had determined that he had been wrong to use the personal account.

“After reviewing his email practices earlier this year, the secretary believes that his previous, occasional use of personal email for work-related business, even for routine administrative issues and backed up to his official account, was a mistake,” said the spokesman, Peter Cook. “As a result, he stopped such use of his personal email and further limited his use of email altogether.”

And why is the use of a government email account to conduct government business such a hurdle for those in the highest level of our government?